Supportive Care Drugs in Oncology
Supportive care drugs manage chemotherapy toxicities including nausea, myelosuppression, pain, and metabolic emergencies to maintain treatment tolerability.
## Overview
Supportive care pharmacology enables cancer patients to tolerate aggressive treatment regimens by preventing and managing treatment-related toxicities. Effective antiemesis, myeloid growth factor support, and pain management are essential components of modern oncology practice.
## Antiemetics
Chemotherapy-induced nausea and vomiting (CINV) is classified as highly emetogenic (HEC, >90% incidence without prophylaxis), moderately emetogenic (MEC, 30-90%), or low/minimal emetogenic.
- **5-HT3 antagonists** (ondansetron, granisetron, palonosetron): Block serotonin receptors on vagal afferents and in the vomiting center. Palonosetron has higher receptor affinity and a 40-hour half-life.
- **NK1 antagonists** (aprepitant, fosaprepitant, netupitant): Block substance P/NK1 receptors in the CNS. Essential for HEC prophylaxis. Aprepitant is a CYP3A4 inhibitor — monitor for drug interactions.
- **Dexamethasone**: Mechanism of antiemetic effect unclear; enhances efficacy of all other antiemetics.
- **Olanzapine**: Added to 3-drug regimen for highly refractory CINV.
## Myeloid Growth Factors
**G-CSF** (filgrastim, pegfilgrastim): Stimulates neutrophil production from bone marrow progenitors. Reduces duration and severity of chemotherapy-induced neutropenia. Pegfilgrastim (PEGylated) has a long half-life, administered once per cycle. Primary prophylaxis when febrile neutropenia risk >20%.
**Erythropoiesis-stimulating agents** (epoetin alfa, darbepoetin): Treat chemotherapy-related anemia (Hgb <10 g/dL); avoid if curable intent treatment (possible tumor-promoting effect).
## Bone-Modifying Agents
Bisphosphonates (zoledronic acid, pamidronate) and denosumab (anti-RANK-L) reduce skeletal-related events (fractures, cord compression, hypercalcemia) in bone metastases. Osteonecrosis of the jaw (ONJ) is a class effect; dental evaluation required before initiating.
## Tumor Lysis Syndrome Prevention
Allopurinol (xanthine oxidase inhibitor) or rasburicase (urate oxidase, degrades existing uric acid) prevent uric acid nephropathy in high-risk patients (Burkitt lymphoma, bulky ALL).
## Key Takeaways
- HEC prophylaxis requires triple therapy: NK1 antagonist + 5-HT3 antagonist + dexamethasone
- Pegfilgrastim provides convenient once-per-cycle G-CSF support; start 24-72h after chemotherapy
- Denosumab and bisphosphonates reduce skeletal events in bone metastases
- Rasburicase (not allopurinol) is preferred for established hyperuricemia and high-risk tumor lysis